1. Field of the Invention
The present invention relates to a member for a mask film, a process for producing a mask film using the member and a process for producing a printing plate of a photosensitive resin using the mask film. More particularly, the present invention relates to a member for a mask film which is advantageously used for producing a mask film used for preparing a printing plate of a photosensitive resin such as a flexographic printing plate, does not require treatments with chemicals, provides excellent resolution by etching with a laser beam and can be used for preparing a printing plate having a great size; a process for producing a mask film using the member; and a process for producing a printing plate of a photosensitive resin using the mask film.
2. Description of Related Art
Printing plates such as flexographic printing plates which are formed by irradiating a photosensitive resin layer of a printing plate material having the photosensitive resin layer with light through a mask film used as a negative film having a desired pattern, followed by removing portions of the photosensitive resin layer not exposed to the light by washing, has heretofore been known.
The mask film used for preparing the printing plate of a photosensitive resin is produced, in general, in accordance with a photographic process using silver salts or various printing processes such as a process using a laser printer. However, these processes cannot be used for preparing a mask having a great size. For example, when a mask having a great size such as the size of a news paper is required, two or more mask films are used and combined together in a manner such that an image is formed without disturbance. Moreover, the photographic process has a drawback in that procedures are complicated since the operations must be conducted in a dark room specific for the photographic process and treatments with a plurality of chemicals are required although the photographic process provides excellent resolution. On the other hand, in the case of the printing process, the operation is simple since a pattern can be formed directly by a printer using digital data. However, the process provided by ZANTE Company (a United States company) using a laser printer has drawbacks in that a treatment with a chemical is necessary to improve the property of a mask film not transmitting light and the resolution is not sufficient.
As the technology using a laser beam in the field of preparing printing plates, for example, a resin printing plate having depressed portions for printing which are formed by irradiating with a laser beam desired portions of a resin layer in a printing plate having the resin layer on the surface so that the desired portions of the resin layer is sublimed or decomposed (Japanese Patent Application Laid-Open No. Heisei 5(1993)-24172) and a printing plate which is formed, using a resin printing plate material having a resin layer sensitive to ionizing radiation and a layer not transmitting ionizing radiation disposed on a substrate, by removing portions of the layer not transmitting ionizing radiation corresponding to a printing image with a laser beam, followed by irradiating the portions of the resin layer sensitive to ionizing radiation corresponding to the portions removed above with ionizing radiation and by subjecting the portions of the resin layer sensitive to ionizing radiation irradiated above to a development treatment (Japanese Patent Application Laid-Open No. Heisei 10(1999)-67088), have been disclosed.
However, in the above technology, a printing plate is prepared by directly irradiating a resin printing plate with a laser beam without using a mask film and the technology is not related to the production of a mask film.